#144788 by Andreas Wolf, spatz4000 and aufumy: missing block clearing on admin index by modules page

modules/system/system.admin.inc

@@ -1842,7 +1842,7 @@ function theme_system_admin_by_module($menu_items) {
     }
   }
 
-  $output = '<div class="admin">';
+  $output = '<div class="admin clear-block">';
   foreach ($container as $id => $data) {
     $output .= '<div class="'. $id .' clear-block">';
     $output .= $data;